Unfortunately, Obsrv wasn’t fully built out yet and failed early in tests. I never got around to testing again but I am considering creating a package of my prototypes and suggestions to hopefully get other designers and researchers to pick up where I left off.
That would work within a WebView, not a Chrome Custom Tab per my tests. Chrome Custom Tabs redirects worked perfectly with App Links, but even then there are chances of it failing, which is why you probably want a simple landing page with a button to redirect to your custom URI scheme as well.
Since I’m building a third-party app, there’s a requirement to redirect users to authorize the connection. This is what the crux of the post was about — performing this authorization in a Chrome Custom Tab.
Once done, you’ll receive a code that you can use for the token exchange. At this stage, you could do this with Account Manager if you want to, or normal API calls.